Method and means for altering apparent perspective of images



May 28, 1963 H. s. HEMSTREET 3,091,662

METHOD AND MEANS FOR ALTERING APPARENT PERSPECTIVE OF IMAGES Original Filed May 27. 1955 5 Sheets-Sheet 1 LIA FIGJZ,

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L B R\ R l G QR z R5 4 FIG B HAROLD $.HEMSTREET lNVENTOR ATTORNEY May 28, 1963 H. s. HEMSTREET 3,091,652

METHOD AND MEANS FOR ALTERING APPARENT PERSPECTIVE OF IMAGES Original Filed May 27. 1955 5 Sheets-Sheet 2 F IG. 3:

SERVO M-3OO HAROLD S. HEMSTRE ET INVENTOR ATTORNEY H. s. HEMSTREET 3,091,662

5 Sheets-Sheet 3 INVENTOR 8: Q3 HAROLD $.HEMSTREET May 28, 1963 METHOD AND MEANS FOR ALTERING APPARENT PERSPECTIVE OF IMAGES Original Filed May 27. 1955 ATTORNEY INVENTOR ATTORNEY 5 Sheets-Sheet 4 mmmm. 03-2 o mum m o 6 K 5a-.

HAROLD S. HEMSTREET H. S. HEMSTREET METHOD AND MEANS FOR ALTERING APPARENT PERSPECTIVE OF IMAGES May 28, 1963 Original Filed May 2'7. 1955 May 28, 1963 H. s. HEMSTREET 3,091,652

METHOD AND MEANS FOR ALTERING APPARENT PERSPECTIVE 0F IMAGES Original Filed May 27. 1955 5 Sheets-Sheet 5 FIG.6

HAROLD S. HEMSTREET INVENTOR ATTORN EY United States Patent Ofifice Patented May 28, 1963 3,091,662 METHOD AND MEANS FUR ALTERING APPAR- ENT PERSPECTIVE F IMAGES Harold S. Hemstreet, Binghamton, N .Y., assignor to General Precision, Inc., a corporation of Delaware Original application May 27, I955, Ser. No. 511,488, now Patent No. 2,975,671, dated Mar. 21, 1961. Divided and this application Apr. 8, I960, Ser. No. 26,924

3 Claims. (Cl. 178-72) This is a division of my copending application Serial No. 511,488, filed May 27, 1955, now Patent No. 2,975,- 671.

This invention relates to method and apparatus for altering the apparent perspective of images. In my copending applications Serial Number 480,033, filed January 5, 1955, for Visual Display Method and Apparatus, and Serial Number 500,325, filed April 11, 1955, for Simulated Viewpoint Displacement Method and Apparatus, there are shown methods and means by which an image having the appearance of an area as viewed from a particular viewpoint may be distorted or altered in apparent perspective so as to provide an image having the appearance of said area as viewed from a difierent viewpoint displaced laterally and/ or vertically in the plane of the particular viewpoint. Application Serial Number 480,- 033 illustrates apparatus comprising a rotatable prism and a variable power anamorphoser, the prism being operable to provide distortion of the type required to simulate lateral displacement of the viewpoint, and the anamorphoser being operable to provide distortion of the type required to simulate vertical displacement of the viewpoint. Application Serial Number 500,325 illustrates improved apparatus for providing the same effect, said improved apparatus comprising in one preferred embodiment a pair of variable power anamorphosers rotatable as a unit about a projection system axis. Using either of the abovementioned systems, objects having the appearance of areas as viewed from given viewpoints may be distorted to provide images simulating the same areas as viewed from different viewpoints. Each of the abovementioned applications shows in considerable detail the inventions as they may be used in conjunction with grounded flight trainers or simulators to provide a realistic visual display of simulated aircraft travel. Motion picture films of a grounded area may be taken from an actual aircraft as it travels with respect to said area along a reference path, or motion pictures may be taken while moving a camera along a miniature reference path in relation to a model ground scene. If such films are then projected upon a screen for observation by a person within a grounded trainer, and if the images of such films are suitably altered in apparent perspective in accordance with the difference between the reference path and the simulated course flown by the grounded trainer, an extremely realistic visual display may be obtained, and such display is of great value in the instruction of aircraft pilots.

The present invention relates to an improvement to the method and apparatus disclosed in application Serial Number 500,325, which uses in a preferred embodiment two variable power anamorpho-sers. As far as I know, variable power anamorphosers are not utilized extensively in much apparatus other than that described above, and hence such optical devices are not always readily available on the market and often must be specially constructed, sometimes at considerable expense. The present invention contemplates in some embodiments use of only a single variable power anamorphoser together with other optical means readily constructed or more available on the market, and hence provides a more economical method and means by which the aforementioned alteration of the apparent perspective of images may be accomplished.

It is therefore an object of the invention to provide improved method and apparatus for providing alteration of the apparent perspective of optical images.

It is a further object of the invention to provide improved apparatus for providing alteration of the apparent perspective of an image which requires the use of a single variable power anamorphoser in conjunction with a conventional variable effective focal length spherical lens.

It is another object of the invention to provide improved electrical method and means for altering the apparent perspective of images.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the apparatus embodying features of construction, combinations of elements and arrangement of parts which are adapted to effect such steps, all as exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention reference should be had to the following detailed description taken in connection with the accompanying drawings, in which:

FIG. 1a is a plan view of a grounded object comprising square with an inscribed circle.

FIG. 1b is an elevation view showing geometrically the views seen at different altitudes of the grounded object of FIG. 1a;

FIG. 2 is a geometrical diagram showing in its left hand portion an elevation view of a viewpoint at a particular altitude and in its right hand portion the views seen at such altitude at five different lateral positions;

FIG. 3 is a geometrical diagram useful in understanding how a variable anamorphoser and a variable power spherical lens may be utilized to provide alteration of the apparent perspective of images;

FIG. 4 is a chart showing the relationship between viewpoint displacement and various control quantities which may be applied to apparatus of the invention to provide viewpoint displacement;

FIG. 5 is an electrical schematic diagram of an exemplary form of analogue computer which may be used to provide semi-automatic control of the apparatus of the invention;

FIG. 6 is a perspective view partially cutaway of an exemplary form of optical apparatus constructed in accordance with the invention;

FIG. 7 is an electrical schematic diagram of an exemplary form of electrical apparatus which may be used in practising the invention.

Assume that a large grounded surface area carries a square ABCD with an inscribed circle I, such as shown in a plan view in FIG. la. If such figures are viewed from any point directly above their common center (i.e. from any point on a line perpendicular in two directions from the plane of the figures), the figures will appear undistorted, or in other words, the viewer will perceive a square and a circle. If such figures are viewed from any other point (i.e., at some other angle than directly above, the viewer will perceive an ellipse and a trapezoid rather than a circle and a square. In the elevation view of FIG. 1b, the figures lie on the ground between points A and B and are observed from three viewpoints, P P and P each of which viewpoints are situated at different altitudes above the ground but each at the same distance R (see FIG. 1a) from the center of the figures. It will be seen that if an observer is located at viewpoint P (an altitude h, above the ground, that the dimension of the figure along axis ZZ will subtend an angle i at the eye of the observer, and that the line of sight (line P P) from the observer to the center of the figures will make an angle m with a horizontal line P P' drawn through.

viewpoint P Similarly, the same dimensions of the figures Will subtend angles and 1 at the eye of the observer when the figures are viewed from viewpoint P (at altitude I1 and viewpoint P (at altitude h and the angles downward from the horizon atwhichthe observer views the figures will be and (0 respectively. Now assume that a large screen S is interposed between the viewpoints and the figures observed. Itwill be seen that if proper images of the grounded figures were present on screen S, that an observer would perceive the same scenes as formerly observed on the, ground. Shown in FIG. 1b are images I I and I which indicate the proper location, size and shape of the images required on screen S, the images having been rotated 90 degrees about the vertical. It should now become apparent thatif suitable images are projected upon a screen for observation by a stationary observer (such. as a student in astationary grounded trainer, for example) thatscenes such as those viewed at various altitudes may be presentedto the-stationary observer, providing the observer with an illusion of apparent location at the various altitudes. For example, if image I is projected onto a screen at an angle 0 downward from a horizontal line drawn through the stationary viewpoint so that it subtends an angle 1 at the eye of the stationary observer, there .will be created an illusion to the observer of seeing the actual figures from viewpoint P at an altitude hg, or if an image such as I is projected at an angle m downwardly from they h0rizontal line drawn through the observers stationary viewpoint so that it subtends an angle 77 at the eye of the stationary observer, he will have the illusionof viewing the grounded image from viewpoint P at an altitude k Any rectangular grounded surface viewed in perspective appears trapezoidal, or otherwise stated, any pair of lines actually parallel appear to. converge at a'vanishing point when viewed in perspective. For example, a flat roadway of great length having actually parallel sides appears in perspective to converge-to a point at the horizon. In FIG. 1/) images I I and I are drawn so that sides AB and CD of each of the images converge at the horizon points P P and P associated with thealtitudes of their respective viewpoints. Since figure ABCD is actually a square (DA=AB) determination of the points at which lines connecting the various viewpoints with parts of square ABCD intersect screen S also deter mines the width of lines DA and CB of each of images I1, I2 and I3. images I I and I have upper and lower bases of equal respective width, indicating that an image of a square'or other grounded object cast for observation on a screen by a stationary observer should not change in width as the image is changed in size, shape andlocation to simulate vertical movement of the observer to a different altitude, but that only the height of such image should, change. From FIG. 1b the height of image I may be determined as follows. The distance from point P to the top of image I may be seen by similar triangles to equal S is.)

The distance from point P to the bottom of the image Thus the required change in height A of an image of s an object to simulate a change in altitude may .be expressed as the difference between Equations 1 and 2, or:

1 1 Ah hZ I R,( (3) 'Since distances-R R and R areconstants for a change in altitude only, with the 'distance from the stationary viewpoint to the screen fixed, it will be seenthat the 'required change in height of theprojected image for simuiated ch'ange in altitude is attraction of altitude change ly- .4

As has beenshown in FIG. lb, the location on the screen of an image of an object must change as altitude changes-in order to. simulate properly the object as seen at a differentaltitude.- Image I' imust be projected downwardly at an angle o from a horizontal line through the stationary observers viewpoint, and hence it will'be seen by similar triangles that the .center of image I willlie on screen S below the horizon line' a distance of By similar analysisthe distance of the center of image I below the horizon line on screen S'Will be'fou'ndto be expressable as RS he Hence as simulated altitude increases, the distance of any point of an image fromthe horizon line on the screen must vary inversely inaccordance with its distance from theh'o'rizon. The proper alteration of an image then, to provide an apparent'change in altitude, is a compressing or stretching of th'eimage with respect to' the observed horizonline. g i l To simulate observationfrom point Pi an altitude h; above the ground of thefgrounded object of FIG. 1 (the side'of which is shownas line'AB in FIG. 2 an image having a height k and location as shown should be cast upon screen S,"as is shown in the left-hand portion of FIG. 2; The right hand portion of FIG. 2 illustrates the proper images which shouldbe projectedon screens to It may be noted that the trapezoids of the right ofcenterline simulate displacement of the viewpoint at five different positions displaced in a horizontal direction parallel to screen S. Image I illustrates the image required to create the-illusion of seeing the grounded object from'altitu de I1 at a point directly above the centerline' ZZ"of the object, and it will be seen that image I is symmetrical about line Image'I illustrates the image'required to create the illusion' of seeing the grounded'object from altitude I2 atapoint' displaced laterally a distance d to Z-Z, and images 1 I and I illustrate the image requiredto' create the illusion of seeing the grounded object from three different points laterally displaced diiferent distances to the left of centerline'Z-Z. I I

' Consider'the differences between images I and'I and '7 i assume that an image suchas I; is projected upon the screen from 'a" slide'or one frame of a motion picture film. I It will become apparentthat if such a projected image could be altered or distorted to provideinstead an image suchas I that a stationary observervie wing thescreen 'would'receive the illusion of' having moved tothe right through distance d. It may be noted that any point on the horizon from altitude h should remain at point 0 regardless of lateral position from which the grounded object is supposed to be viewed, It may also i be noted that the distance of any point on image I to a perspective of an image to provide an imagehaving the corresponding point on image I is directly proportional to the simulated viewpoint displacement distance dfand inversely proportional to'the distance of such point'from the horizon. Such distortion or alteration of the apparent appearance of being viewed from a laterally displaced viewpoint is termed shear distortion, since it is analogous to the distortion produced by applying pure shear forces to an elastic member.

Thus it may be seen that by providing distortions of the types explained above in connection with FIGURES 1 and 2 that both vertical and lateral displacent of a viewpoint may be simulated. My copending application Serial N-umber 480,033 illustrates in a preferred embodiment at variable anamorphoser and a rotatable prism which independently produce vertical and shear distortion of the required nature, and copending application Serial Number 500,325 illustrates in a preferred embodiment a pair of crossed variable anamorphosers which cooperatively produce the desired change in apparent perspective of an image.

Referring to FIG. 3a there is shown a rectangle ABCD having a height h. Assume that the rectangle outlines a portion of an image representing a scene viewed at an altitude h from a viewpoint located on the centerline of the rectangle. Recalling the above analysis from FIGS. 1 and 2 it will be seen that the parallelogram of FIG. 3a may represent the same image portion viewed from an altitude I1 at a viewpoint displaced laterally a distance d from the original viewpoint associated with the rectangle. Assuming that the upper line of the rectangle (also the upper line of the parallelogram) represents the horizon or vanishing point portion of the image, it will be seen that the parallelogram of FIG. 3a may be formed by (l) stretching the rectangle with respect to the horizon line in accordance with the change in altitude between the viewpoints, and (2) by shearing the image in an amount proportional to lateral distance between the viewpoints, while maintaining the horizon portion of the image in its original form.

In FIG. 3b there is shown rectangle ABCD representing an image having the appearance of an area as viewed from an original altitude from a reference lateral position. Also shown is a parallelogram A'BC'D' corresponding to the parallelogram of FIG. 3a, but the parallelogram of FIG. 3b has been rotated through an angle p with respect to the rectangle. The operation of the invention is to receive an image such as that represented by the rectangle of FIG. 3b and to stretch or compress and shear the image to provide an image such as is represented by the parallelogram AB'C'D of FIG. 3b. The altered image may then be rotated and shifted, if desired, so that the vanishing point or horizon portion of the image will be located in its original position. The further rotation and shifting will ordinarily be desirable when the invention is used to provide simulation of continuous displacement of the viewpoint.

Assume that the image represented by rectangle ABCD is projected along an optical axis having its center at 0. Also assume that direction XX and direction YY of FIG. 3b are respectively the horizontal and vertical axes of the image. If an anamorphoser is inserted in the optical system, the rectangle image will be magnified more along one axis than along a second perpendicular axis. For example, if an anamorphoser were used which had a power greater than unity along axis YY and a power of unity along axis X-X, the rectangle would be increased in height. If an anamorphoser is inserted so that its axes of magnification do not correspond to the horizontal and vertical axes of the image, the image will be sheared. Assume that an anamorphoser is inserted in the optical system to operate upon the image of rectangle ABCD with the greater than unity power of the anamorphoser acting along axis MA and with a unity power along axis LL perpendicular to axis MA. Axis MA is shown in FIG. 3b rotated through an angle ti from vertical axis YY of the original image. Dimensions of the original rectangle image along axis MA will then be increased, while dimensions of the original image along axis LL will remain the same, resulting in a parallelogram image. In FIG. 3b if the power of the anamorphoser along axis MA is assumed to be 2, the image produced by the anamorphoser will correspond to large parallelogram A"B"C"D", wherein dimensions along axis MA are double the corresponding dimensions of the rectangle, and dimensions along axis LL of both figures are the same.

Now assume that a spherical lens is inserted into the optical system to operate upon the distorted image represented by large parallelogram A"BCD. The spherical lens may be made to image the parallelogram image upon a screen or other surface. If the focal length or magnification of such a spherical lens is properly selected, the resultant image cast upon the screen may be made to correspond with parallelogram ABCD' of FIG. 31), since it will be apparent that parallelogram A'B'C'D is merely a reduced copy of parallelogram A"B"C"D". In order for resultant image ABCD to represent the original image as viewed from a different viewpoint in the manner discussed above, the vanishing line or horizon portions of the original and the altered figures must be the same size. Thus in FIG. 3b, if line CD of the rectangle represents the horizon portion of the projected image, line CD of parallelogram ABCD must be the same length as line CD. Since the length of side C"D" of parallelogram image A"B"C"D depends upon the length of side CD of the original image, the power of the anamorphoser along axis MA and the angular orientation of the anamorphoser with respect to the original rectangle image (i.e., the value of angle 5) it will be seen that the focal length or magnification required in the spherical lens to provide a resultant image of proper size for focus upon a surface at a fixed distance is a function of the angle {3 and the power M of the anamorphosers along axis MA. Therefore, if the spherical lens mentioned above actually comprises a variable effective focal length lens combination, provision of the proper magnification for various values of ,8 and M will provide an image on the surface or screen bearing the correct size relation.

As mentioned above, in systems wherein it is desirable to provide distortion to simulate continuous viewpoint displacement it is desirable to maintain the horizon portion of an image fixed on a screen or viewing surface. Since use of the anamorphoser-variable focal length lens combination serves to rotate the image through the angle p as shown in FIG. 3b, it is necessary in such systems to provide a counter-rotation. In optical systems of relatively small angular field, such as systems utilizing the invention to slant lettering or designs, the necessary counter-rotation may be efiected such as by use of Dove prisms, as will be readily apparent to those skilled in the art. In systems requiring a larger angular field, I prefer to provide the counter-rotation by rotating the object and anamorphoscr through the angle p. As well as providing the counter-rotation through the angle p, it is necessary in some systems to shift the resultant image laterally and/or vertically on the screen or other surface if it is considered desirable to maintain image portions representing the horizon or vanishing line at a fixed location as viewpoint displacement is continuously varied. Such shifting will be required in any such system if the vanishing point or horizon of the original image is not projected along the optical axis of the system. The shifting required is explained in detail in my copending application Serial Number 503,211, filed April 22, 1955, for Method and Apparatus for Producing Visual Display, and means and method are shown therein which may be used for providing the desired shifting in systems constructed in accordance with the present invention. It will become apparent from comparison of FIGS. 3a and 3b that to align horizon line CD of the distorted rectangle with line CD of the original or rectangle image, that in addition to providing counter-rotation that parallelogram AB'CD must be shifted leftwardly and upwardly. It may also be seen that if the horizon or vanishing line portion of the original image were a hori- 7 l zontal linepassing through the opticalaxis O of the system, that the distortion of the rectangle image by the anamorphoser and variable focal length spherical lens would not displace such portion of the imagefrom the system axis, and hence no shifting of the distorted image would then be necessary. Therefore, if the object utilized was made so that its portion representing the vanishing point is aligned with the system optical axis, or if the object is shifted so that its vanishing point portion is aligned with the system axis, the resultant projected and distorted image will have its vanishing point portion suitably located. Throughout the specification and claims, the word magnification is intended to include magnification less than unity power as well as magnification greater than unity power. i I

Thus it will be seen that an anamorphoser and a spherical lens may be utilized to distort an image so as to alter its apparent perspective, and to ,cast' a projected image upon a screen or other surface. Since the required powers of the anamorphoser and the spherical lens are different for different amounts of viewpoint displacement, I have provided a variable power anamorphoser and a'variable effective focal length lens in the invention. The relationship between an undistorted image and a resultant distorted image are discussed in terms of viewpoint displacement in connection with FIGS. 1 and 2. vThe relationships between the undistorted andthe distorted images in terms of the powers and orientation of the optical elements are shown geometrically in FIGS. 3a andSb. By analysis of FIGS. 3a and 3b, a number of relationships between the distorted and undistorted images may be determined, utilizing three known relationships: (1) the ratio of the heights I1 11 of the rectangle, (2) the angleof slant on, and (3) the fact that the vanishing point or horizon dimension of both figures is the same/ By straightforward trigonometry which need not be set forth herein, equations may be written which express various relationships of FIGS. 3a and 3b in terms of viewpoint displacement.

In order to provide automatic control of the invention 7 from inputs which are functions of viewpoint displacement, equations may be written which express the variables M (power of the anamorphoser), P (power of the variable spherical lens), and [3 (the angular orientation of the anamorphoser with respect to the object), or instead functions of such variables in terms of viewpoint displacement. If it is considered desirable topr'ovide theabovementioned counter-rotation to maintainvanishing point positions of the images coincident, an equation containing the counter-rotation angle p or a function thereof may be written. The equations may be plotted against vertical and lateral viewpoint displacement to provide charts such as FIG. 4. The equations also may be solved simultaneously by means of interconnected servos in a manner well known in the analogue computer art, but since'the dynamic behavior of such simultaneous equation solvers having many interconnecting loops is usually quite diflicult to analyze, it is usually deemed preferable to solve the simultaneous equations analytically for the control variables required. The following equations may be derived from FIGS. 3a and 3b:

Expressions 1 and 2' may beseen to r eci te required con. trol quantities (m, B in terms of viewpoint displacement It' to b'e emphasized that iwhilethelabove expressions accurately set forth relationshipslbetween the required control vari'ablesfand i that {while such equations are de'e ed tob'e inf a convenient'form for analogue computer 'qlii l n t a t qse' sk d, n h v o uter a ma d y i efn eq v e texp ons andl i j ert h p cationswhere ohly'limited viewpoint displacement is to be simulated accurately, that various'termsin the equations having.minoretfect'over the range of intended operation maybe neglected without prohibitivee'rror. f I FIGURE 4illustrat'es in graphic form the general nature of the"relatior1'ships'between power and orientation of the distortion apparatus and viewpoint displacement. Expression 1 given above'for m may be seen to beam expression defining a circle, and "in 'FI G. 4 there are shown six plotsof Expression 1 plotted on vertical displacement h and lateral displacement d coordinates" in the plane of the objectQ Inspection of Expression l orFlG. 4 indicates thatvalues'of constant anamorphoser power are circles of varying diameter all .having'their centers spacedat different points along the d o axisr' Assume that in FIG. 4 the horizontal line'labelled 11 indicates the altitude or vertical position from 'whicha film wastaken. The various m circles then indicate the required anamorphoser power to simulate displacement "of the viewpoint to points correspondingito' the"respective plotted values. For example, ifthe viewpointV is 'to be'fsim'ulated, an anamorphoser power m equal tolcgis requireds 1 Plots 'of Expression 2 "for twelve various values k degrees through k degrees) of constant 3 (anamorphoser orientation with respect to the object) yield circles of the type partially'shown in FIG. 4, and partial plots of Expression 3 for three values (k through km) of spherical r'n'agnification P provide plots as shown. The'curves of constant anamorphoser angle 5 may be seen to becir- ,cles of varying diameter all havi'ng their centers, located at' various points along the h=o line, with each circle passing through the original viewpoint position V. The curves of constant spherical magnification P may be seen to comprise hyperbolasih'aving their centers located at the al=o,h=0 point. Plots of Expression 5' for various values of p may. bema'de; resulting in' the straight line's shown for 'nine dilrerent values (k through k of counter-rotation angle" Assume .that an object represents an image as viewed frornpoint V. I If it is desired to provide distortion of an image of the object to simulate observation from point V located below point V and laterally displaced to the right, inspection of FIG. 4 will reveal that the required anamorphoser m power is approximately 'k j'the'required angular rotation 5 between the anamorphoser "and the object is k' degrees, the 'required value of spherical magnification P is approxiniatelyg'equalto k and: the required counter-rotation angle p is midway between #:k and p= k degrees. With charts such a's'th'atof FIG. 4,the powers and rotations for any desired viewpoint may be determined, and then the apparatus may be manually or automatically positioned to such powers and angles. Dials and scales may be provided in conventional manner on the apparatus of FIG. 7 to facilitate adjustment of the various elements to the desired positions. It should be recognized that the plots shown in FIG. 4 are all partial plots, and complete plots should be provided for determination of required control quantities for more widely varying viewpoints. It should also be remembered that the distances d and h are measured in the plane of the viewpoint.

Shown in FIG. in electrical schematic form is an exemplary form of analogue computer which may be utilized to receive input quantities in terms of viewpoint displacement to provide output quantities to control the optical elements of the invention, and those skilled in the art will recognize that the system shown is an analogue computer mechanization of Equations 1a, 2a, 3a and 5a. Viewpoint displacement input quantities are shown applied to the computer of FIG. 5 by means of manually-positioned potentiometer control knobs 501, 502 and 503, but those skilled in the art will readily recognize that such inputs may be automatically controlled. Apparatus suitable for providing such inputs automatically when the invention is used in conjunction with a grounded aircraft trainer is shown in both of my copending applications Serial Number 480,033 and Serial Number 500,- 325.

A constant potential excites potentiometer R-501, the arm of which i positioned by the h input quantity, applying an h potential to excite potentiometer R-502, the arm of which is similarly positioned, thereby providing an I2 potential on the arm of potentiometer R-502. This potential is applied via summing resistor 11-503 to summing amplifier U-501. In similar manner i2 and d potentials are derived by cascaded potentiometer pairs R-504, R505 and R-506, R-507, and these potentials are applied to amplifier U-501 via summing resistors R-508 and R-509, respectively. The sum of such applied potentials, inverted in polarity by amplifier U501 is applied to excite potentiometer R510, the arm of which is positioned by m servo M400, applying a potential commensurate with the second term of Equation la to the input circuit of servo M400 via resistor R513. A potential proportional to h hg is derived by means of potentiometer R-S ll and R-5r12, and applied via summing resistor R5l4 to the servo M-100 input circuit. The h h potential is also applied to excite a cascaded pair of potentiometers R-515 and R-516, the arms of which are positioned by the M-100 servo, deriving a potential proportional to the first term of Expression la. Servo M4100 continuously positions itself so that the sum of the applied input potentials is maintained at zero, thereby solving Equation la and providing a shaft output position commensurate with m, the power of the variable anamorphoser. The shaft output quantity may be connected to position the anamorphoser at the required anamorphic magnification by means of gear 510, as shown in FIG. 6.

Since servos M-200, -M-300 and M-400 each solve Equations 2a, 3a and 5a in an analogous manner, a detailed explanation of each circuit is deemed to be unnecessary. For sake of clarity resolvers utilized to derive the sine and cosine potentials are shown schematically as simple potentiometers, but in actual practice comprise conventional resolvers capable of 360 degree resolution. Buffer amplifiers usually utilized in such computer circuits to minimize loading errors have not been shown. Each of the servos shown may comprise any conventional analogue computer servo, and may utilize electrical, hydraulic, or mechanical motive means, and either A.C. or DC. computation may be utilized. Summing amplifiers shown schematically may comprise the well-known Swartzel summing amplifier circuit or well known series addition circuits may be substituted. It may be noted that servo M-200 provide an output shaft position commensurate with 20. Those skilled in the art will recognize that the variable anamorphoser may be driven by such a shaft output in accordance with B by a 2:1 gear reduction. Each servo may include conventional tachometer generator or other rate feedback for stabilization, and may be equipped in conventional fashion with speed reduction gearing mechanical limit stops. Those skilled in the art will recognize that in a servo solving a quadratic equation, selection of the proper direction of operation of the servo motive means is necessary for the servo to select the proper root of the quadratic equation. For example, if a conventional two-phase servomotor is utilized in servo M-100, the polarity connection of the quadrature winding of the motor will determine which root the servo will select. While the position of servo M300 is determined by the position of servo M- (because of the potential from potentiometer R-526), the converse is not true, so that the system can be made stable by conventional technique with minimum difficulty. Servo M-200 orients the variable power anamorphoser with respect to the film or other object, servo M-300 adjusts the variable power spherical lens to the required positions, and servo M-400 provides the required counter-rotation to maintain vanishing point positions of the images coincident regardless of the viewpoint displacement being simulated, all as shown in FIG. 6.

Referring now to FIG. 6 there is shown a projector PR which may comprise, for example, a conventional slide projector or motion picture projector, depending on the nature of the use to be made of the invention. Mounted coaxially with the optical axis of the projector are a variable power spherical lens (indicated generally at Z) and a variable power anamorphoser lens combination (indicated generally at V). If desired, the position of the two units may be interchanged, so that the anamorphoser first acts on the projected images. The variable power spherical lens may comprise, for example, four spherical lens elements axially adjustable one pair to another such as shown in US. Patent No. 2,566,485 to Cuvillier, although many other variable eifective focal length lenses may be used. Although the Cuvillier unit is shown in Patent 2,566,485 for use on a camera and is afocal, it will be readily apparent to those skilled in the art that it may be used as shown and adapted to focus on a screen placed at a finite distance. The composite lens comprises a pair of lenses L and L; which are axially movable with respect to fixed lenses L and L Lenses L and L are slidably mounted in lens barrel 601, and carry pins 602 and 603, which protrude through a longitudinal slot cut in lens barrel 60 1. Rotatable sleeve 604 surrounds lens barrel 601, and cam slots 605, 606 cut in sleeve 604 accommodate pins 602 and 603. A toothed flange portion of sleeve 604 is engaged by gear 607, so that rotation of servomotor M-300 rotates sleeve 604, axially moving lenses L and L; with respect to lenses L and L It will be apparent to those skilled in the art that by providing appropriate non-linear slots 605 and 606, the variation in power of zoom lens Z may be made linear with respect to rotation of motor M-300. For sake of clarity, potentiometers, tachometer generators, and associated equipment driven by the servomotors has not been shown in FIG. 6.

The variable anamorphoser lens combination shown at V may comprise one of a number of different variable anamorphosers, but is illustrated as comprising a variable power anamorphoser of the type shown and explained in detail in my copending application Serial Number 480,033. Such variable anamorphoser comprises two positive cylindrical lenses L and L which are axially movable with respect to a fixed negative cylindrical lens L Positive lenses L and L are carried in lens holders 610 and 611 which are slidably carried in lens barrel 612 and axially constrained against rotation by means of keyway 613. Cam pins 614 and 615 attached to lens holders 610 and 611 protrude through a longitudinal slot in lens barrel 612 and are cammed by means of cam slots "616 and 6E7 cut in rotatable sleeve 6 18, movingpositive lenses L and L axially with respectto negative lens L As shown in FIG. 6, each of the cylindrical lensesi has its direction of anamorphic power aligned with the others. Servo motor M-lthi rotates gear filtlwhich meshes with toothed flange 620 of sleeve 618, thereby rotating sleeve 618 aboutlens barrel 612. in order to orient angrilarly the variable anamorphoser with respect'to the optical axis, the variableanamorphoser isrotatably supported in bearings '621, 621, and 2p 'ser'vomotor Mdtiti positions the anamorphoser by means of bevelgea'r 622, which meshes with beveled portion" 623 of lens barrel 612. Other types of variable anamorphosers which may be utilized are, for example, the ti-Lux Val type of variable anamorphoser which is made' by Projection Optics Co.', of Rochester, N.Y'., and the fSuper'Panatar and Ultra Panatar types of variable anamorphoser, which latter devices are made by Radiant Manufacturing Corpo ration, of Chicago, Illinois. 1 I

A cover (not shown) may be placed over the apparatus if desired. Servomotor M460, which provides the counter-rotation of the distorted imagein those systems in which such rotation is necessary, has not been shown in FIG. 6. in embodiments of the invention inwhich the images are projected upon a fixed screen, servomotor M- 400 may be mechanically connected to rotate the object and anamorphoser around the optical'axis, or to rotate Dove prisms in such system where a limited angular field is allowable. In systems utilizing a single or only several objects, such objects may be rotated relative to the projector in which they are utilized. In systems using a large number of images (such as motion picture systems), it is deemed preferable to rotate the entire projector'about its optical axis in order to avoid mechanical complication of the projector film feed andfilm storage mechanism. In embodiments of the invention Where'it is desirable to maintain vanishing point portions of images coincident on a surface as viewpoint displacement is varied, but where the angular orientation of the distorted image with respect to space need not be fixed,'servomotor M-4tl0 may be mechanically connected torotate the surface about the system optical axis; As mentionedabove, if vanishing point portions of an image are to remain in one place on the projection surface as the amount'of vie point displacement is varied, the optical axis of the anamorphoser and the zoom lens should'be maintained directed toward the vanishing point portionof the object, or the entire projection apparatus may be'angularly rotated to shift the projected image as set forth in detail in my copending application Serial Number 503,211; Shown in FIG. 7 is a schematic'diagram of anelectrical system which may be utilized in practising thc'invention. A projector indicated within dashed lines at 701 comprises a light source 702, a 'collimating lens 7&3, a projection lens 7&4 and a reflector 7&6. An image of object 705 is cast upon the face of a conventional television pickup or camera tube 707 comprised with video signal generating means indicated generally at 793. Camera tube 767 is provided with conventional horizontal and vertical scanning means 711, which means are actuated in conventional manner by the output potentials of horizontal and vertical scanning generators 7tl9 and 710, respectively. The video signal thereby produced by the camera tube is amplified by video amplifiers indicated generally at 712 and applied between gridand cathode of a conventional projection cathode raytube 713. Acceleration potentials (not shown) are applied to cathodc ray tube 713 in conventional manner. The sawtooth vertical sweep potential output from'vertical scanning generator 710 is applied via potentiometers Ri701 and R402, and amplifier 716 to conventional vertical defiection means 718 carried ontube 713. The sawtooth horizontal sweep potential output from horizontal scanv. a a 12 a ning' generator 799,3 appii'edvia potentiometer iR 70 3 and amplifier 717 to thej hori'z on tal' deflectionmeansffl? of tube 713; It will be'apparent that if like s'wee'p' p o tentials were a'ppliedfto botlr'c'amera' tube and cathode ray tube','that'the picture which will appear on theiface ofthelcathode'ra'ytube would be a substantial duplicate of that projected onto camera tube 707; '1 Howeverfa relative rotation through "the anglefijis introduced,between'the projector and the video 'signal generating'means bymeans of 2B servo M ztitk'fThe output shaft of servo NI-203' is applied through reduction gearing'7l4 "to mec nical differential 715, so th'atfthe direction of vertical 'sw'eep on camera tube 797 is-atian angie'ot 'fi withiresp'ect' to thevertical ax'is of objec't 7tl 5 Then i as the arm of I potentiometei R 7 01 is positioned" by servo Mlfillin accordancei'with anamorphic i power in, the magnitude of thefve'rtical 'sweepfpoteiitial applied to vertical deflection "means 718 of 'pictu reff tubef 71'3 controlled, therebycompressing or expanding the picture on tube 713 in a manner similar to that of the, variable 'anamorphos'erf Both horizontal and 'yertical fsw'eep potentials applied-to tube 713 farecont'rolled inmagnitude by P servo Mifit) by means'of potentiometersRfltB and 11-702, respectively: Since these two potentiometers may selected "solas'f'to' expand uniformly'or compress'uni- "formly" the picture on tube 713, it will be seenjthat they "produce ari'efiectsimilar' to that 'of'a variablepower spherical lens, Thus it will be seen that a picture may be produced on the" face of i 713 similar to that produced by the optical apparatusof FIG. Ifdesired,'tube713 maybe rotated to maintain vanishing point portions of an"imageprojectedfrom 713 coincident on, a screen regardless of viewpoint displacement' This may be done by rotating 'thepicturetube defiection coils, or the' entire picture tube thr'ough the angle-(,8+ such as by driving the picture tube from the output-of a mechanical'differential (not shown) having shaft inputs drive'nfroin 2B servo M 2tl0 and 5 servo M-tii). "'Itwill'be recognized bythose skilled in theart that-the relative sweep amplitudes'betwee'n camerafitub'e and picture'tube determine picture distortion, and'hence in an alternative embodiment of the invention, tl'l e 'pictur'e tube may be -'-driven wit .fsWe'epf 'pot en'tials ioff uniform accomplished byfvaryprojection cathoderay tube amplitude, and distortion may be ing'theamplitude of thecamera scanning'potential accordance with desired viewpoint displacement.

As a result of this disclosure it will immediately become apparent to those skilled 'in the art thafa number'of known expedients mayfbe utilized in conjunction withthe invention. For; example, a conventional spherical wide angle attachment may be added t'othe optic'al systemillustrated i'norder to p'rovide a'iarger angular fieldf Th e power of such a' wide angleattachmentwillaffect"the images projected'in 'the's'ame manner as the p'csw'erbftae "zoom lens shown, and in constructing a compiitent b control theinvention; those skiliedin the art wnrr'eeognize that the-Wide angle attachment power setting may be scaledirfas a simple modification of the poweror' focal length of the zoom lens. Any difference between" the projection system focal length and the camera focal length 'erfects the size of the ultimate'image, so that the ratio f I," I

of camera'focal'length to projectorfocal lengthv should alsobe considered as a scale' factor in constructing the P computer M490. I twill also become apparent lto those skilled in, the artthat an image may bejcompressed anamorphically a fixed, amount .in constructing ,the, ob ject and thenexpanded an equal amount during projection in order to obtainthe'usualadvantages of-TCinemascope? projection. 'Whilei the' 'invention has'been shown as used in conjunction with film images, it will'he readily apparent that it may be used with equal facility with, images from other transparenciesandalso with reflected images.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained. Since certain changes may be made in carrying out the above method and in the constructions set forth Without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. Apparatus for altering the apparent perspective of an image, comprising: signal generating means responsive to an applied image, said signal generating means having a pair of perpendicularly disposed scanning means and operative to produce video signals, means for generating sweep potentials to operate each of said scanning means, means for introducing a relative rotation between said applied image and said signal generating means, cathode ray tube means responsive to said video signals to produce an image, said cathode ray tube having a pair of perpendicularly-disposed deflection means responsive to sweep potentials synchronized with the scanning sweep potentials, means to vary the relative amplitudes between the potentials applied to one scanning means and one deflection means, and means to vary the relative amplitudes between the potentials applied to the other scanning means and both deflection means.

2. Apparatus for altering the apparent perspective of an image, comprising: signal generating means responsive to an applied image, said signal generating means having a pair of perpendicularly disposed scanning means and operative to produce video signals, means for generating sweep potentials to operate each of said scanning means, means for introducing a relative rotation between said applied image and said signal generating means, cathode ray tube means responsive to said video signals to produce an image, said cathode ray tube having a pair of perpendicularly-disposed deflection means responsive to sweep potentials synchronized with the scanning sweep potentials, first sweep conditioning means to vary the relative amplitudes between the potentials applied to one scanning means and one deflection means, second sweep conditioning means to vary the relative amplitudes between the potentials applied to the other scanning means and both deflection means, and means for so controlling said first and second sweep conditioning means that each point of the image on said cathode ray tube is displaced from the position it would occupy if said relative amplitudes were unvaried by an amount proportional to the distance of said position from the horizon of the image which would be produced on said cathode ray tube if said relative amplitudes were unvaried.

3. Apparatus for altering the apparent perspective of an image, comprising: signal generating means responsive to an applied image, said signal generating means having a pair of perpendicularly disposed scanning means and operative to produce video signals, means for generating sweep potentials to operate each of said scanning means, means for introducing a relative rotation between said applied image and said signal generating means, cathode ray tube means responsive to said video signals to produce an image, said cathode ray tube having a pair of perpendicularly-disposed deflection means responsive to sweep potentials synchronized with the scanning sweep potentials, first Sweep conditioning means to vary the relative amplitudes between the potentials appiied to one scanning means and one deflection means, second sweep conditioning means to vary the relative amplitudes between the potentials applied to the other scanning means and both deflection means, and means for so controlling said first and second sweep conditioning means that each point of the image on said cathode ray tube is displaced from the position it would occupy if said relative amplitudes were unvaried by an amount proportional to the distance of said position from the horizon of the image which would be produced on said cathode ray tube if said relative amplitudes were unvaried, the points on a first side of said horizon being parallely displaced.

References Cited in the file of this patent UNITED STATES PATENTS 1,921,464 Harries Aug. 8, 1933 2,098,390 Iams Nov. 9, 1937 2,510,670 Trott June 6, 1950 

1. APPARATUS FOR ALTERING THE APPARENT PERSPECTIVE OF AN IMAGE, COMPRISING: SIGNAL GENERATING MEANS RESPONSIVE TO AN APPLIED IMAGE, SAID SIGNAL GENERATING MEANS HAVING A PAIR OF PERPENDICULARLY DISPOSED SCANNING MEANS AND OPERATIVE TO PRODUCE VIDEO SIGNALS, MEANS FOR GENERATING SWEEP POTENTIALS TO OPERATE EACH OF SAID SCANNING MEANS, MEANS FOR INTRODUCING A RELATIVE ROTATION BETWEEN SAID APPLIED IMAGE AND SAID SIGNAL GENERATING MEANS, CATHODE RAY TUBE MEANS RESPONSIVE TO SAID VIDEO SIGNALS TO PRODUCE AN IMAGE, SAID CATHODE RAY TUBE HAVING A PAIR OF PERPENDICULARLY-DISPOSED DEFLECTION MEANS RESPONSIVE TO SWEEP POTENTIALS SYNCHRONIZED WITH THE SCANNING SWEEP POTENTIALS, MEANS TO VARY THE RELATIVE AMPLITUDE BETWEEN THE POTENTIALS APPLIED TO ONE SCANNING MEANS AND ONE DEFLECTION MEANS, AND MEANS TO VARY THE RELATIVE AMPLITUDES BETWEEN THE POTENTIAL APPLIED TO THE OTHER SCANNING MEANS AND BOTH DEFLECTION MEANS. 